Electrochromic devices on non-rectangular shapes

ABSTRACT

Bus bar configurations and fabrication methods for non-rectangular shaped (e.g., triangular, trapezoidal, circular, pentagonal, hexagonal, arched, etc.) optical devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

An Application Data Sheet is filed concurrently with this specificationas part of the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed Application Data Sheet is incorporated by referenceherein in its entirety and for all purposes.

FIELD

Embodiments disclosed herein generally relate to optically switchabledevices such as electrochromic devices, and more particularly to methodsof fabricating optically switchable devices.

BACKGROUND

Electrochromic (EC) devices are typically multi-layer stacks including(a) at least one layer of electrochromic material that changes itsoptical properties in response to the application of an electricalpotential, (b) an ion conductor (IC) layer that allows ions, such aslithium ions, to move through it, into and out from the electrochromicmaterial to cause the optical property to change, while preventingelectrical shorting, and (c) transparent conductor layers, such astransparent conducting oxides (TCOs), over which an electrical potentialis applied to the electrochromic layer. In some cases, the electricpotential is applied from opposing edges of an electrochromic device andacross the viewable area of the device. The transparent conductor layersare designed to have relatively high electronic conductance properties.Electrochromic devices may have more than the above-described layerssuch as ion storage or counter electrode layers that optionally changeoptical states.

Due to the physics of the device operation, proper functioning of theelectrochromic device depends upon many factors such as ion movementthrough the material layers, the electrical potential required to movethe ions, the sheet resistance of the transparent conductor layers, andother factors. Size and shape of the electrochromic device play animportant role in the uniformity of coloration across the face of thedevice. Additionally, the size and shape of the device play a role inthe transition of the device from a starting optical state to an endingoptical state (e.g., from colored to bleached state or bleached tocolored state). The conditions applied to drive the transitions and holdan optical end state can have quite different requirements for differentshaped devices.

Further, where an electrochromic device is of a non-rectangular shape,certain fabrication processes are more difficult. For example, laseredge delete (LED) and bus bar pad expose (BPE) operations utilizesquare/rectangular laser patterns which are oriented parallel orperpendicular to the local edge of the substrate. These patterns aredefined by vector files that are implemented by the scanner/laser. Whilethese patterns lend themselves to simple processing withrectangular-shaped devices, they are much more difficult to implement onshapes that are more complex, for example shapes having curved edges oredges that are at non-right angles to adjacent edges.

SUMMARY

Certain embodiments described herein pertain to bus bars configurationsfor non-rectangular shaped optically switchable devices (e.g.,triangular-shaped, trapezoidal-shaped, shaped with curved portions,etc.). These bus bars are designed to deliver electrical potential tothe device in a manner that equalizes, to the extent possible, theeffective voltage over the entire face of the device. In doing so, thesebus bars may provide a uniform ending optical state and smooth andspeedy optical transitions across the face of the device withouthotspots. In some embodiments, the bus bars are positioned and sizedlengthwise so that the distance to both bus bars is equalized, to theextent possible, across the device surface. Various techniques foraccomplishing this result will be described herein.

In another aspect, certain embodiments herein relate to methods ofperforming laser edge delete and bus bar pad expose operations onnon-rectangular shaped electrochromic devices. These methods may includeusing a non-rectangular laser pattern (e.g., a circular laser pattern)and/or a rectangular laser pattern oriented in a direction that is notparallel to a side of the substrate that forms two right angles withadjacent sides of the substrate. The latter laser pattern is sometimesreferred to herein as an angled laser pattern. It may be appropriate foruse in performing edge deletion or bus bar pad exposure operations ofnon-rectangular windows such as triangular windows, trapezoidal windows,pentagonal windows, hexagonal windows, and other polygonal windows. Inthe case of a right triangular shaped window, an angled laser patternmay be used to perform edge deletion and/or bus bar pad exposure alongthe edge of the window forming a hypotenuse.

Certain embodiments relate to an optically switchable window comprisinga non-rectangular optically switchable device comprising a first side, asecond side, and a third side adjacent the second side. The opticallyswitchable window further comprises a first bus bar spanning a firstportion along a first side of the non-rectangular optically switchabledevice. The optically switchable window further comprises a second busbar spanning a second portion of a second side of the non-rectangularoptically switchable device, the second side opposing the first side. Inthese embodiments, the first bus bar and second bus bar are configuredto apply voltage to the optically switchable device.

Certain embodiments relate to a method of determining a bus barconfiguration for an optically switchable device having anon-rectangular shape. In these embodiments, the method comprisesdetermining a centroid of the non-rectangular shape; determining firstand second anchor points on a first side and second side of thenon-rectangular shape based on the determined centroid; determininglengths of a first bus bar segment and a second bus bar segmentextending from the first anchor point and lengths of a third bus barsegment and a fourth bus bar segment extending from the second anchorpoint, wherein a first bus bar comprises the first bus bar segment andthe second bus bar segment, and wherein the second bus bar comprises thethird bus bar segment and the fourth bus bar segment; determining asummed minimum bus bar distance as a distance of a weakest coloringpoint on the optically switchable device to the first bus bar and adistance of the weakest coloring point to the second bus bar;determining a summed minimum bus bar distance of a distance of astrongest coloring point on the optically switchable device to the firstbus bar and a distance of the strongest coloring point to the second busbar; calculating a difference between the summed maximum bus bardistance and the summed minimum bus bar distance; adjusting the lengthsof the first bus bar segment, the second bus bar segment, the third busbar segment, and the fourth bus bar segment until the calculateddifference reaches convergent lengths for each of the first, second,third, and fourth bus bar segments; and using the convergent lengths ofthe first bus bar segment, the second bus bar segment, the third bus barsegment, and the fourth bus bar segment to determine a bus barconfiguration for the optically switchable device.

Certain embodiments relate to a method of fabricating an opticallyswitchable device on a substrate. The method comprises receiving at alaser tool said substrate having disposed thereon one or more layers ofthe optically switchable device and directing a laser spot according toa non-rectangular laser pattern onto a region of the opticallyswitchable device proximate one or more edges of the substrate to removeat least one of the one or more layers of the optically switchabledevice at the region. In some cases, the method further comprisesrepeating the direct the laser spot operation to direct the laser spotat different regions of the optically switchable device proximate theone or more edges of the substrate to define a portion of the substratewhere at least one of the one or more layers is removed.

Certain embodiments relate to a method of fabricating an opticallyswitchable device on a non-rectangular substrate having at least oneedge that does not form a right angle with an adjacent edge, saidnon-rectangular substrate having disposed thereon one or more layers ofthe optically switchable device. The method comprises (a) receiving at alaser tool said non-rectangular substrate; (b) directing a laser spotfrom the laser tool onto the one or more layers at a region of thesubstrate proximate the at least one edge that does not form a rightangle with an adjacent edge to thereby remove the one or more layers atthe region; and (c) repeating operation (b) at different regions of thesubstrate proximate the edge or edges of the substrate to define aportion of the substrate where at least one of the one or more layers isremoved. In these embodiments, the laser spot is rectangular in shapeand having two sides parallel to the at least one edge.

Certain embodiments relate to an apparatus for fabricating an opticallyswitchable device on a non-rectangular substrate having at least oneedge that does not form a right angle with an adjacent edge, saidnon-rectangular substrate having disposed thereon one or more layers ofthe optically switchable device. The apparatus comprises a laser tooland a scanner configured to perform the operations of: (a) receiving ata laser tool said non-rectangular substrate; (b) directing a laser spotfrom the laser tool onto the one or more layers at a region of thesubstrate proximate the at least one edge that does not form a rightangle with an adjacent edge to thereby remove the one or more layers atthe region; and (c) repeating operation (b) at different regions of thesubstrate proximate the edge or edges of the substrate to define aportion of the substrate where at least one of the one or more layers isremoved. In these embodiments, the laser spot is rectangular in shapeand having two sides parallel to the at least one edge. In one case, thelaser tool has a dove prism.

Embodiments include EC devices fabricated using methods describedherein.

These and other features and embodiments will be described in moredetail below with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic drawing of a top view of a rectangularelectrochromic device with a planar bus bar arrangement.

FIG. 1B is a simplified plot of the local voltage values at eachtransparent conductive layer as a function of position across theelectrochromic device.

FIG. 1C is a simplified plot of V_(eff) as a function of position acrossthe electrochromic device.

FIG. 2 is a graph depicting voltage and current profiles associated withdriving an electrochromic device from bleached to colored and fromcolored to bleached.

FIG. 3 is a graph depicting certain voltage and current profilesassociated with driving an electrochromic device from bleached tocolored state.

FIG. 4 is a schematic diagram of a top view of a rectangularelectrochromic device with a planar bus bar arrangement.

FIG. 5 is a schematic diagram of a top view of a right trapezoid shapedelectrochromic device with a planar bus bar arrangement, according to anembodiment.

FIG. 6 is a schematic diagram of a top view of a right triangle shapeddevice with a bus bar configuration, according to embodiments.

FIG. 7 is a schematic diagram of a top view of a right trapezoid shapeddevice with bus bars in a first configuration along the right angle andthe opposing leg, according to embodiments.

FIG. 8 is a schematic diagram of a top view of a right trapezoid shapeddevice with bus bars in a second configuration having a first bus baralong a first base and a second bus bar along a second base and adjacentleg, according to embodiments.

FIG. 9 is a schematic diagram depicting a first method for selecting abus bar configuration for a right trapezoid shaped device, according toembodiments.

FIG. 10 is a schematic diagram depicting a second method for selecting abus bar configuration for a right trapezoid shaped device, according toembodiments.

FIG. 11 is a flowchart depicting a second method for determining lengthsof bus bars, according to embodiments.

FIG. 12 is a schematic diagram showing the application of a method ofdetermining a bus bar configuration to a right triangle and two righttrapezoids, according to embodiments.

FIGS. 13A-13C are schematic diagrams showing solutions for acceptablebus bar layouts for a right triangle and two right trapezoids, accordingto embodiments.

FIGS. 14A, 14B, 15, 16, 17, and 18 are examples of bus bar layoutsdesigned with technique(s) described herein according to embodiments.

FIG. 19-23 are plots of V_(eff) and coloration in triangular-shapedelectrochromic devices having different bus bar ratios, according toembodiments.

FIG. 24A is a flowchart of a process flow describing aspects of a methodof fabricating an electrochromic device, according to certainembodiments.

FIG. 24B depicts top views illustrating steps in the process flowdescribed in relation to FIG. 24A.

FIG. 24C depicts top views of devices similar to that described inrelation to FIG. 24B.

FIG. 24D illustrates cross-sections of the electrochromic lite describedin relation to FIG. 24B.

FIG. 24E depicts top views illustrating steps in the fabrication of around electrochromic device.

FIG. 25A shows a portion of an electrochromic device where a singlerectangular laser pattern was used to remove material from the surfaceof the device.

FIG. 25B shows two adjacent rectangular patterns that may be used toremove material from the surface of an electrochromic device.

FIG. 26 illustrates a trapezoid shaped lite and its orientation througha laser tool on its first and second passes through the tool.

FIG. 27 depicts a single circular pattern that may be utilized inaccordance with various embodiments.

FIGS. 28A and 28B depict a semi-circular lite and two differentcombinations of patterns that may be used in accordance with certainembodiments.

FIG. 29 shows a single angled pattern that may be utilized in accordancewith certain embodiments herein.

FIG. 30 illustrates a trapezoid shaped lite having angled and non-angledrectangular laser patterns in accordance with various embodiments.

FIG. 31 depicts an ablation pattern having a saw-toothed edge.

FIG. 32 shows an embodiment where fiber rotation is used to rotate theorientation of a pattern on a substrate.

FIG. 33 shows an embodiment where prism rotation is used to rotate theorientation of a pattern on a substrate.

FIG. 34 shows an exemplary dove prism that may be used in accordancewith certain embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the presented embodiments.The disclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments will be described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

Definitions

An “optically switchable device” can refer to a thin device that changesoptical state in response to electrical input. It reversibly cyclesbetween two or more optical states. Switching between these states iscontrolled by applying predefined current and/or voltage to the device.The device typically includes two thin conductive layers (e.g.,transparent conductive oxide layers or “TCOs”) that sandwich at leastone optically active layer. The electrical input driving the change inoptical state is applied to the thin conductive layers. In certainimplementations, the input is provided by bus bars in electricalcommunication with the conductive layers. While the disclosureemphasizes electrochromic devices as examples of optically switchabledevices, the disclosure is not so limited. Examples of other types ofoptically switchable devices include certain electrophoretic devices,liquid crystal devices, and the like. In certain cases, the opticallyswitchable device is disposed over a substantially transparent substratesuch as glass. Optically switchable devices may be provided in variousoptically switchable products, such as optically switchable windows.However, the embodiments disclosed herein are not limited to switchablewindows. Examples of other types of optically switchable productsinclude mirrors, displays, and the like. In the context of thisdisclosure, these products are typically provided in a non-pixelatedformat; that is, having a monolithic switchable device coating.

An “optical transition” can refer to a change in any one or more opticalproperties of an optically switchable device. The optical property thatchanges may be, for example, tint, reflectivity, refractive index,color, etc. In certain embodiments, the optical transition will have adefined starting optical state and a defined ending optical state. Forexample, the starting optical state may be 80% transmissivity and theending optical state may be 50% transmissivity. The optical transitionis typically driven by applying an appropriate electric potential acrossthe two thin conductive layers of the optically switchable device.

A “starting optical state” can refer to the optical state of anoptically switchable device immediately prior to the beginning of anoptical transition. The starting optical state is typically defined asthe magnitude of an optical state which may be tint, reflectivity,refractive index, color, etc. The starting optical state may be amaximum or minimum optical state for the optically switchable device;e.g., 90% or 4% transmissivity. Alternatively, the starting opticalstate may be an intermediate optical state having a value somewherebetween the maximum and minimum optical states for the opticallyswitchable device; e.g., 50% transmissivity.

An “ending optical state” can refer to the optical state of an opticallyswitchable device immediately after the complete optical transition froma starting optical state. The complete transition occurs when opticalstate changes in a manner understood to be complete for a particularapplication. For example, a complete tinting might be deemed atransition from 75% optical transmissivity to 10% transmissivity. Theending optical state may be a maximum or minimum optical state for theoptically switchable device; e.g., 90% or 4% transmissivity.Alternatively, the ending optical state may be an intermediate opticalstate having a value somewhere between the maximum and minimum opticalstates for the optically switchable device; e.g., 50% transmissivity.

A “bus bar” can refer to an electrically conductive material, e.g. ametal tape or strip, metallized ink or similar material used for suchapplications, electrically connected to a conductive layer such as atransparent conductive electrode of an optically switchable device. Thebus bar delivers electrical potential and current from a lead to theconductive layer. An optically switchable device may include two or morebus bars, each connected to one or more conductive layers of the device.In various embodiments, a bus bar is illustrated in the form of a lineand spans at least a portion of a side of the device. Often, a bus baris located near the edge of the device.

“Applied Voltage” or V_(app) can refer to the difference in electricalpotential (e.g., voltage potential) applied by bus bars of oppositepolarity to the electrochromic device. Each bus bar may be electricallyconnected to a separate transparent conductive layer. The appliedvoltage may have different magnitudes or functions such as driving anoptical transition or holding an optical state. Between the transparentconductive layers are sandwiched the optically switchable devicematerials such as electrochromic materials. Each of the transparentconductive layers experiences a potential drop between the positionwhere a bus bar is connected to it and a location remote from the busbar. Generally, the greater the distance from the bus bar, the greaterthe potential drop in a transparent conducting layer. The localpotential of the transparent conductive layers is often referred toherein as the V_(TCL). Bus bars of opposite polarity may be laterallyseparated from one another across the face of an optically switchabledevice.

“Effective Voltage” (V_(eff)) can refer to the potential between thepositive and negative transparent conducting layers at any particularlocation on the optically switchable device. In Cartesian space, theeffective voltage is defined for a particular x,y coordinate on the faceof the device. At the point where V_(eff) is measured, the twotransparent conducting layers are separated in the z-direction (by thedevice materials), but share the same x,y coordinate. As describedelsewhere herein, transitioning optical state at an area of anelectrochromic device is dependent on the effective voltage, V_(eff), atthat area. The effective voltage, V_(eff), at that area depends on theapplied voltage V_(app) delivered by the bus bars, the distance of thearea to the bus bars, and the material properties (e.g., L, J, R, etc.)of the electrochromic device.

“Hold Voltage” can refer to the applied voltage necessary toindefinitely maintain the device in an ending optical state.

“Drive Voltage” can refer to the applied voltage provided during atleast a portion of the optical transition. The drive voltage may beviewed as “driving” at least a portion of the optical transition. Itsmagnitude is different from that of the applied voltage immediatelyprior to the start of the optical transition. In certain embodiments,the magnitude of the drive voltage is greater than the magnitude of thehold voltage. An example application of drive and hold voltages isdepicted in FIG. 3.

“Laser Pattern” can refer to a vector file or other instructions, aswell as an associated shape of a laser cutting region on a substratesurface. The vector file or other instructions may be used to programthe movement of a laser's focus area over the surface of a device. Thesepatterns are used to define the area over which material is removedduring a laser edge delete or bus bar pad expose operation, for example.The laser pattern is a unit of material removal that is repeated overmultiple positions on the substrate surface to remove a significantlylarger amount of material (e.g., a bus bar pad expose region or an edgedelete region). In various embodiments, the field of view of the lasercutting tool applying the laser pattern limits the laser pattern size.In a typical embodiment, the laser pattern has a dimension (e.g., a sideor diameter) that is on the order of millimeters (e.g., about 5 to 100millimeters).

INTRODUCTION

Driving a color transition in a typical electrochromic device isaccomplished by applying a voltage potential delivered by separated busbars on the device. If such a device has a rectangular shape, it may bedesirable to position two bus bars perpendicular to the shorter sides(along the longer parallel sides) in a planar configuration such asillustrated in FIG. 1A. This planar configuration in a rectangularshaped device may be desirable because the transparent conducting layersused to deliver an applied voltage/current over the face of the thinfilm device have an associated sheet resistance, and this bus bararrangement allows for the shortest span over which current must travelto cover the entire area of the device, thus lowering the time it takesfor the conductor layers to be fully charged across their respectiveareas, and thus lowering the time to transition the device to a newoptical state.

While an applied voltage, V_(app), is delivered by the bus bars,essentially all areas of the device see a lower local effective voltage,V_(eff), due to the sheet resistance of the transparent conductinglayers and the ohmic drop in potential across the device. The center ofthe device (the position midway between the two bus bars) frequently hasthe lowest value of V_(eff). This may result in an unacceptably smalloptical switching range and/or an unacceptably slow switching time inthe center of the device. These problems may not exist at the areasnearer to the bus bars. This is explained in more detail below withreference to FIGS. 1B and 1C.

FIG. 1A shows a top view of a rectangular electrochromic lite 100including bus bars in the planar configuration. The electrochromic lite100 comprises a first conductive layer 110, a second conductive layer,120, and an electrochromic stack (not shown) between first conductivelayer 110 and second conductive layer 120. Other layers may be included.Electrochromic lite 100 also includes a first bus bar 105 disposed onfirst conductive layer 110 and a second bus bar 115 disposed on secondconductive layer, 120. As shown, first bus bar 105 may extendsubstantially along one side of first conductive layer 110 near an edgeof the electrochromic lite 100. Second bus bar 115 may extendsubstantially along one side of second conductive layer 120 opposite theside of electrochromic lite 100 on which first bus bar 105 is disposed.Some devices may have extra bus bars, e.g., along all four sides. Afurther discussion of bus bar configurations and designs, includingplanar configured bus bars, is found in U.S. patent application Ser. No.13/452,032, titled “ANGLED BUS BAR,” filed on Apr. 20, 2012, which isincorporated herein by reference in its entirety.

FIG. 1B is a graph showing a plot of the local voltage V_(TCL) appliedto first transparent conductive layer 110 and the local voltage V_(TCL)applied to second transparent conductive layer 120 that drives thetransition of electrochromic lite 100 from a bleached state to a coloredstate, for example. Curve 125 shows the local values of the voltageV_(TCL) in first transparent conductive layer 110. As shown, the voltagedrops from the left “L” hand side (e.g., where first bus bar 105 isdisposed on first conductive layer 110 and where the voltage is applied)to the right “R” hand side of the first conductive layer 110 due to thesheet resistance and current passing through first conductive layer 110.Curve 130 shows the local voltage V_(TCL) in second conductive layer120. As shown, the voltage increases (becomes less negative) from theright hand side (e.g., where second bus bar 115 is disposed on secondconductive layer 120 and where the voltage is applied) to the left handside of second conductive layer 120 due to the sheet resistance ofsecond conductive layer 120. The value of the applied voltage, V_(app),in this example is the difference in voltage values between the rightend of the curve 130 and the left end of curve 125. The value of theeffective voltage, V_(eff), at any location between the bus bars is thedifference in values of curves 130 and 125 at the position on the x-axiscorresponding to the location of interest.

FIG. 1C is a graph showing a curve of V_(eff) values across theelectrochromic device between first and second conductive layers 110 and120 of electrochromic lite 100. As explained, the effective voltage,V_(eff) is the local voltage difference between the first conductivelayer 110 and the second conductive layer 120. Regions of anelectrochromic device subjected to higher effective voltages transitionbetween optical states faster than regions subjected to lower effectivevoltages. As shown, the effective voltage is the lowest at the center ofelectrochromic lite 100 (e.g., “M” location) and highest at the edges ofelectrochromic lite 100, closer to the bus bars. The voltage drop acrossthe device is due to ohmic losses as current passes through the device.The device current is a sum of the electronic current and ionic currentin the layers capable of undergoing redox reactions in theelectrochromic device. The voltage drop across large area electrochromicdevice in a window can be alleviated by including additional bus barswithin the viewing area of the window, in effect dividing one large areaelectrochromic device into multiple smaller electrochromic devices whichcan be driven in series or parallel. However, this approach may not beaesthetically appealing due to the contrast between the viewable areaand the bus bar(s) in the viewable area. That is, it may be much morepleasing to the eye to have a monolithic electrochromic device withoutany distraction from bus bars within the viewable area.

As described above, as a window size increases, the electronicresistance to current flowing across the thin faces of the transparentconductive layers (TCL) layers, such as first conductive layer 110 andthe second conductive layer 120 also increases. This resistance may bemeasured between the points closest to the bus bar and in the pointsfarthest away from the bus bars (referred to as the centroid of thedevice in the following description). When current passes through a TCL,the voltage drops across the TCL face, reducing the effective voltage atthe center of the device. This effect is exacerbated by the fact thattypically as window area increases, the leakage current density for thewindow stays constant but the total leakage current increases due toincreased area. Both of these may cause the effective voltage at thecenter of the electrochromic window to fall substantially, which cancause a noticeable reduction in the performance observed ofelectrochromic windows, especially for windows that are larger than, forexample, about 30 inches across. This issue can be addressed by using ahigher V_(app) such that the center of the device reaches a suitableeffective voltage.

Typically the range of V_(eff) allowable for safe operation (i.e.,operation with reduced risk of damage or degradation of device) of solidstate electrochromic devices is between about 0.5V and 4V, or moretypically between about 1V and about 3V, e.g., between 1.1V and 1.8V.These are local values of V_(eff). In one embodiment, an electrochromicdevice controller or control algorithm provides a driving profile whereV_(eff) is always below 3V, in another embodiment, the controllercontrols V_(eff) so that it is always below 2.5V, in another embodiment,the controller controls V_(eff) so that it is always below 1.8V. Theserecited voltage values refer to a time averaged voltage (where theaveraging time is of the order of time required for small opticalresponse, e.g., a few seconds to few minutes).

An added complexity of operation of an electrochromic window is that thecurrent drawn through the electrochromic device is not fixed over theduration of the optical transition (i.e., the transition period).Instead, during the initial part of the transition, the current throughthe device is substantially larger (up to 30× larger) than in the endingoptical state when the optical transition is complete or nearlycomplete. The problem of poor coloration at the center of the device isparticularly noticeable during this initial part of the transitionperiod, as the value of V_(eff) at the center is significantly lowerthan what it will be at the end of the transition period.

For a rectangular electrochromic device with planar bus bars (i.e., busbars in a planar configuration such as those shown in FIG. 1A and FIG.4), V_(eff) across the electrochromic device can be described generallyby the following:

ΔV(0)=V _(app) −RJL ²/2  (Equation 1a)

ΔV(L)=V _(app) −RJL ²/2  (Equation 1b)

ΔV(L/2)=V _(app)−3RJL ²/4  (Equation 1c)

where:

-   -   V_(app) is voltage difference applied to bus bars driving        electrochromic device;    -   ΔV(0) is V_(eff) at bus bar connected to first transparent        conducting layer;    -   ΔV(L) is V_(eff) at bus bar connected to second transparent        conducting layer;    -   ΔV(L/2) is V_(eff) at center of the device, midway between the        two planar bus bars;    -   R=transparent conducting layer sheet resistance;    -   J=instantaneous current density; and    -   L=distance between the two planar bus bars of the electrochromic        device.

The transparent conducting layers are assumed to have substantiallysimilar, if not the same, sheet resistance for the calculation. Howeverthose of ordinary skill in the art will appreciate that the applicablephysics of the ohmic voltage drop and local effective voltage stillapply even if the transparent conducting layers have dissimilar sheetresistances (e.g. one TCL is a metal oxide, while the other TCL is atransparent metal layer).

Certain embodiments described herein pertain to controllers and controlalgorithms for driving optical transitions in optically switchabledevices (e.g., electrochromic devices) having planar bus bars. In suchdevices, substantially linear bus bars of opposite polarity may bedisposed at opposing sides of a rectangular or other polygon shapedelectrochromic devices. Some embodiments described herein pertain tocontrollers and control algorithms for driving optical transitions inoptically switchable devices employing non-planar bus bars. Such devicesmay employ, for example, angled bus bars disposed at vertices of thedevice. In such devices, the bus bar effective separation distance, L,is determined based on the geometry of the device and bus bars. Adiscussion of bus bar geometries and separation distances may be foundin U.S. patent application Ser. No. 13/452,032, titled “Angled Bus Bar”,and filed Apr. 20, 2012, which is incorporated herein by reference inits entirety.

As R, J or L increase, V_(eff) across the device decreases, therebyslowing or reducing the device coloration during transition and/orreducing device coloration in the final optical state. Referring toEquations 1a-1c, the V_(eff) across the window is at least RJL²/2 lowerthan V_(app). It has been found that as the resistive voltage dropincreases (due to increase in the window size, current draw etc.) someof the loss can be negated by increasing V_(app). However, V_(app)should remain sufficiently low to ensure that V_(eff) at the edges ofthe device is maintained below a threshold value where reliabilitydegradation could occur.

In summary, it has been recognized that both transparent conductinglayers experience ohmic drop, and that this drop increases with distancefrom the associated bus bar, and therefore V_(TCL) decreases withdistance from the bus bar for both transparent conductive layers. As aconsequence, V_(eff) decreases in locations removed from both bus bars.

To speed along optical transitions, the applied voltage can be initiallyprovided at a magnitude greater than that required to hold the device ata particular optical state in equilibrium. This approach is illustratedin FIGS. 2 and 3.

FIG. 2 shows a current/voltage profile for an electrochromic device inaccordance with certain embodiments. FIG. 2 shows current profile andvoltage profile for an electrochromic device employing a simple voltagecontrol algorithm to cause an optical state transition cycle (colorationfollowed by bleaching) of the electrochromic device. In the illustratedgraph, total current density (I) is represented as a function of time.As mentioned, the total current density is a combination of the ioniccurrent density associated with an electrochromic transition andelectronic leakage current between the electrochemically activeelectrodes. Many different types of electrochromic devices will have thedepicted current profile. In one example, a cathodic electrochromicmaterial such as tungsten oxide is used in conjunction with an anodicelectrochromic material such as nickel tungsten oxide in the counterelectrode. In such devices, negative currents indicate coloration of thedevice. In one example, lithium ions flow from a nickel tungsten oxideanodically coloring electrochromic electrode into a tungsten oxidecathodically coloring electrochromic electrode. Correspondingly,electrons flow into the tungsten oxide electrode to compensate for thepositively charged incoming lithium ions. Therefore, the voltage andcurrent are shown to have a negative value.

The depicted profile results from ramping up the voltage to a set leveland then holding the voltage to maintain the optical state. The currentpeaks 201 are associated with changes in optical state, i.e., colorationand bleaching. Specifically, the current peaks represent delivery of theionic charge needed to color or bleach the device. Mathematically, theshaded area under the peak represents the total charge required to coloror bleach the device. The portions of the curve after the initialcurrent spikes (portions 203) represent electronic leakage current whilethe device is in the new optical state; that is, current leakage acrossthe ion conductor layer or region due to it being imperfectlyelectrically insulating.

In the figure, a voltage profile 205 is superimposed on the currentcurve. The voltage profile follows the sequence: negative ramp (207),negative hold (209), positive ramp (211), and positive hold (213). Notethat the voltage remains constant after reaching its maximum magnitudeand during the length of time that the device remains in its definedoptical state. Voltage ramp 207 drives the device to its new the coloredstate and voltage hold 209 maintains the device in the colored stateuntil voltage ramp 211 in the opposite direction drives the transitionfrom colored to bleached states. In some switching algorithms, a currentcap is imposed. That is, the current is not permitted to exceed adefined level in order to prevent damaging the device (e.g., driving ionmovement through the material layers too quickly can physically damagethe material layers). The coloration speed is a function of not only theapplied voltage, but also the temperature and the voltage ramping rate.

FIG. 3 illustrates a current/voltage profile for an electrochromicdevice in accordance with certain embodiments. In the depictedembodiment, a current/voltage control profile for the electrochromicdevice employs a voltage control algorithm to drive the transition froma bleached optical state to a colored optical state (or to anintermediate state). To drive the electrochromic device in the reversedirection, from a colored state to a bleached state (or from a morecolored to less colored state), a similar but inverted profile is used.In some embodiments, the voltage control profile for going from coloredto bleached is a mirror image of the one depicted in FIG. 3.

The voltage values depicted in FIG. 3 represent the applied voltage(V_(app)) values. The applied voltage profile is shown by the dashedline. For contrast, the current density in the device is shown by thesolid line. In the depicted profile, V_(app) includes four components: aramp to drive component 303, which initiates the transition, a V_(drive)component 313, which continues to drive the transition, a ramp to holdcomponent 315, and a V_(hold) component 317. The ramp components areimplemented as variations in V_(app) and the V_(drive) and V_(hold)components provide constant or substantially constant V_(app)magnitudes.

The ramp to drive component is characterized by a ramp rate (increasingmagnitude) and a magnitude of V_(drive). When the magnitude of theapplied voltage reaches V_(drive), the ramp to drive component iscompleted. The V_(drive) component is characterized by the value ofV_(drive) as well as the duration of V_(drive). The magnitude ofV_(drive) may be chosen to maintain V_(eff) with a safe but effectiverange over the entire face of the electrochromic device as describedabove.

The ramp to hold component is characterized by a voltage ramp rate(decreasing magnitude) and the value of V_(hold) (or optionally thedifference between V_(drive) and V_(hold)). V_(app) drops according tothe ramp rate until the value of V_(hold) is reached. The V_(hold)component is characterized by the magnitude of V_(hold) and the durationof V_(hold). Actually, the duration of V_(hold) is typically governed bythe length of time that the device is held in the colored state (orconversely in the bleached state). Unlike the ramp to drive, V_(drive),and ramp to hold components, the V_(hold) component has an arbitrarylength, which is independent of the physics of the optical transition ofthe device.

Each type of electrochromic device will have its own characteristiccomponents of the voltage profile for driving the optical transition.For example, a relatively large device and/or one with a more resistiveconductive layer will require a higher value of V_(drive) and possibly ahigher ramp rate in the ramp to drive component. Larger devices may alsorequire higher values of V_(hold). U.S. patent application Ser. No.13/449,251, titled “CONTROLLER FOR OPTICALLY-SWITCHABLE WINDOWS,” filedApr. 17, 2012, and incorporated herein by reference in its entirety,discloses controllers and associated algorithms for driving opticaltransitions over a wide range of conditions. As explained therein, eachof the components of an applied voltage profile (ramp to drive,V_(drive), ramp to hold, and V_(hold), herein) may be independentlycontrolled to address real-time conditions such as current temperature,current level of transmissivity, etc. In some embodiments, the value ofeach component of the applied voltage profile is set for a particularelectrochromic device (having its own bus bar separation, resistivity,etc.) and does not vary based on current conditions. In other words, insuch embodiments, the voltage profile does not take into accountfeedback such as temperature, current density, and the like.

As indicated, all voltage values shown in the voltage transition profileof FIG. 3 correspond to the V_(app) values described above. They do notcorrespond to the V_(eff) values described above. In other words, thevoltage values depicted in FIG. 3 are representative of the voltagedifference between the bus bars of opposite polarity on theelectrochromic device.

In certain embodiments, the ramp to drive component of the voltageprofile is chosen to safely but rapidly induce ionic current flowbetween the electrochromic layer and the counter electrode. As shown inFIG. 3, the current in the device follows the profile of the ramp todrive voltage component until the ramp to drive portion of the profileends and the V_(drive) portion begins. See current component 301 in FIG.3. Safe levels of current and voltage can be determined empirically orbased on other feedback. U.S. Pat. No. 8,254,013, filed Mar. 16, 2011,issued Aug. 28, 2012 and incorporated herein by reference in itsentirety, presents examples of algorithms for maintaining safe currentlevels during electrochromic device transitions.

In certain embodiments, the value of V_(drive) is chosen based on theconsiderations described above. Particularly, it is chosen so that thevalue of V_(eff) over the entire surface of the electrochromic deviceremains within a range that effectively and safely transitions largeelectrochromic devices. The duration of V_(drive) can be chosen based onvarious considerations. One of these ensures that the drive potential isheld for a period sufficient to cause the substantial coloration of thedevice. For this purpose, the duration of V_(drive) may be determinedempirically, by monitoring the optical density of the device as afunction of the length of time that V_(drive) remains in place. In someembodiments, the duration of V_(drive) is set to a specified timeperiod. In another embodiment, the duration of V_(drive) is set tocorrespond to a desired amount of ionic charge being passed. As shown,the current ramps down during V_(drive). See current segment 307.

Another consideration is the reduction in current density in the deviceas the ionic current decays as a consequence of the available lithiumions completing their journey from the anodic coloring electrode to thecathodic coloring electrode (or counter electrode) during the opticaltransition. When the transition is complete, the only current flowingacross device is leakage current through the ion conducting layer. As aconsequence, the ohmic drop in potential across the face of the devicedecreases and the local values of V_(eff) increase. These increasedvalues of V_(eff) can damage or degrade the device if the appliedvoltage is not reduced. Thus, another consideration in determining theduration of Varve is the goal of reducing the level of V_(eff)associated with leakage current. By dropping the applied voltage fromV_(drive) to V_(hold), not only is V_(eff) reduced on the face of thedevice but leakage current decreases as well. As shown in FIG. 3, thedevice current transitions in a segment 305 during the ramp to holdcomponent. The current settles to a stable leakage current 309 duringV_(hold).

Techniques for Equalizing V_(eff) Across Optically Switchable Devices

Optically switchable devices should operate such that coloration orother optical property is as uniform as possible across the entire faceof the device after transition. In other words, device ending opticalstates should exhibit relatively uniform coloration or other opticalproperty. Further, such devices should transition between optical statessmoothly without creating hotspots. A hotspot can refer to a region onthe device where the effective voltage is sufficiently high to possiblydamage or decrease the reliability of the device at the hotspot.

These goals can be realized by bus bar configurations that deliverelectrical potential to the device in a manner that equalizes, to theextent possible, the effective voltage over the entire face of thedevice. This equalization of the effective voltage, V_(eff), isparticularly important for the ending optical states of the device.However, it is also important during optical transitions of the device.For devices having rectangular shapes, equalization of the effectivevoltage, V_(eff), can be accomplished relatively easily. As describedelsewhere herein, one approach is to employ a planar bus barconfiguration in a rectangular device. In a planar configuration, afirst bus bar is placed at the edge of the longest side and a second busbar is placed at the edge of the side opposite the longest side. FIG. 1Aand FIG. 4 show rectangular devices having planar bus barconfigurations. Since the longer opposing sides of a rectangle areparallel by definition, bus bars along these parallel sides can deliverelectrical potential to the device that at least substantially equalizeseffective voltage across the face of the rectangular device. For deviceshaving non-rectangular shapes, equalizing the effective voltage torealize these goals can be more challenging. Triangles, trapezoids,shapes having curved sides (e.g., arch shape, semicircular, quartercircular, etc.), and the like are among some of the more challengingshapes.

FIG. 5 is a top down view of a right trapezoidal shaped electrochromicdevice. In this illustration, a planar bus bar configuration typicallyused for rectangular devices is applied to a trapezoid-shapedelectrochromic device. That is, a first bus bar BB₁ is applied to theedge of the longest side and a second bus bar BB₂ is applied to the edgeof the opposing side. Since these sides are not parallel, the bus barsalong these sides are not parallel and the distance between the bus barsvaries from side “A1” to side “B1” (the sides without bus bars). Side“A1” is longer than side “B1.” At side “A1,” the distance between thebus bars is 50 inches and at side “B1” the distance between the bus barsis 25 inches. This non-uniformity in the distance between the bus barscan provide non-uniform effective voltage, V_(eff), across the device,which can lead to non-uniform coloration of the device. This aspect isdemonstrated in FIG. 5. As shown, the coloration of the device isdarkest (optical transition more progressed) proximal side “B1” wherethe distance between the bus bars is shortest and the V_(eff) ishighest. The coloration of the device is lightest (optical transitionless progressed) proximal side “A1” where the distance between bus barsis at a maximum and the V_(eff) is at a minimum. In some cases, theV_(app) applied to the bus bars could be increased to raise the V_(eff)near “A1” to a level high enough to provide uniform coloration acrossthe device. However, raising the V_(app) could create an undesirablehotspot in areas closer to the shorter side “B1,” which may increase therisk of damaging the device. These adjustments to try to equalize theV_(eff) in the non-rectangular device with a planar bus barconfiguration can potentially lead to over-driving the shorter side “B1”and/or under-driving the longer side “A1.” Although certain dimensionsare shown in the devices of the illustrated embodiments, otherdimensions apply.

This application describes solutions for placement and lengthwise sizingof bus bars to meet the goals of uniform ending optical states andsmooth and speedy optical transitions while minimizing or eliminatinghotspots. In some embodiments, this is accomplished by configuring thebus bars so that the distance to both bus bars is equalized, to theextent possible, across the device surface while maintaining a highratio of the total bus bar length to the device perimeter. Varioustechniques for accomplishing this result will be described herein. Thesesolutions can be applied to non-rectangular (e.g., triangular,trapezoidal, arch-shaped, circular, quarter circular, etc.) shapedoptically switchable devices. Some techniques employ a multi-step methodthat applies to different shape types (e.g., triangles, trapezoids,arches, etc.). Other techniques provide design constraints forparticular types of shapes. Such constraints may define the generallocations and lengths of bus bars on a particular shaped device.

One technique is to apply a perspective transformation method on thenon-rectangular shape. This method linearly transforms thenon-rectangular shape into an effective rectangular shape. A planar busbar configuration can then be designed for the effective rectangularshape. The method then applies an inverse transformation on theeffective rectangular shape with the associated planar bus bars todetermine a bus bar layout for the non-rectangular shape. Thetransformation and inverse transformation steps may be applied multipletimes if desired. One type of transformation that can be used is anaffine transformation, which may preserve straight lines. If an affinetransformation exists for non-rectangular shape to a rectangular shape,then this technique can be applied to determine critical distance of thedevice. In some cases, the affine transformation preserves lengthinformation as well.

Other methods accomplish effectively the same result using symmetry ofthe non-rectangular shape to determine bus bar configurations. Somemethods determine a bus bar configuration that reduces or minimizes theshortest distance from the bus bars to the weakest coloration point (or“weakest point”) on the face of the device. This distance can bereferred to as the critical bus bar distance. The weakest point istypically the centroid of the shape. Likewise the strongest coloringpoint (or “strongest point”) of the device is the shortest distancebetween opposing bus bars. Bus bar distance is defined by the sum of thedistances between a point and each of the two bus bars.

FIG. 6 is a schematic diagram of a top view of a right triangle shapedoptically switchable device with a bus bar configuration designed toequalize, to the extent possible, the effective voltage across the faceof the device, according to embodiments. In some cases, thisconfiguration may be based on minimizing the difference between thecritical bus bar distance and the shortest distance between opposing busbars. In FIG. 6, a first bus bar, BB₁, is located along the hypotenuseof the right triangle and a second bus bar, BB₂, is located along thetwo legs (leg 1 and leg 2) at the right angle opposite the hypotenuse.The length of leg 1 is x and the length of leg 2 is y. The centroid ofthe right triangle is at (x/3, y/3). The hypotenuse forms an angle, θ,with leg 1. The length of the hypotenuse=√{square root over (x²+y²)}.The critical bus bar distance is (min(x,y)+x sin θ)/3. The lengths ofthe bus bars can be adjusted to reduce or minimize the critical bus bardistance. In the illustration, the BB₁ runs to the LED region and thevertical portion of BB₂ along leg 2 is 0.6y and the horizontal portionof BB₂ along leg 1 is 0.6x. In other embodiments, other lengths may beused. In one embodiment, the length of BB₁ may be in the range of0.5√{square root over (x²+y²)} to 1.0√{square root over (x²+y²)}. In oneembodiment, the length of BB₁ may be in the range of 0.8√{square rootover (x²+y²)} to 0.9√{square root over (x²+y²)}. In one embodiment, thelength of the portion of BB₂ along leg 2 may be in the range of 0.4y to1.0y. In one embodiment, the length of the portion of BB₂ along leg 1may be in the range of 0.4x to 1.0x. In one embodiment, the length ofthe portion of BB₂ along leg 2 may be in the range of 0.4y to 0.80y. Inone embodiment, the length of the portion of BB₂ along leg 1 may be inthe range of 0.4x to 0.80x. In one embodiment, the length of the portionof BB₂ along leg 2 may be in the range of 0.5y to 0.7y. In oneembodiment, the length of the portion of BB₂ along leg 1 may be in therange of 0.5x to 0.7x. These lengths and others may be determined frommethods described herein, such as the method described with reference toFIG. 11. In some embodiments, the bus bar lengths may be chosen to avoidoverlapping the edge scribes.

FIG. 7 is a drawing of a top view of a right trapezoid shaped devicewith bus bars in a first configuration (Configuration 1). In FIG. 7, theright trapezoid includes two parallel sides, Base 1 and Base 2, and twoother sides, Leg 1 and Leg 2. A first bus bar, BB₁, is located along theleg 1 and a second bus bar, BB₂, is located along both base 1 and leg 2at the right angle of the right trapezoid. The length of base 1 is h,the length of leg 2 is y, and the length of base 2 is h₁. Leg 1 forms anangle, θ, with Base 1. The centroid of the right trapezoid is at (h/3,(h tan θ)/3). This bus bar configuration of FIG. 7 is similar in certainways to the configuration for the right triangle shaped device shown inFIG. 6. For example, the bus bar configurations in both FIG. 6 and FIG.7 include a bus bar located along a right angle portion and another busbar located at an opposing side.

In FIG. 7, the bus bars are designed to equalize, to the extentpossible, the effective voltage over the face of the device, accordingto embodiments. In some cases, this configuration may be based onminimizing the difference between the critical bus bar distance and theshortest distance between opposing bus bars. For the trapezoid describedin FIG. 7, the critical bus bar distance=(min(h₁ tan θ, y)+(h sin θ))/3.To reduce or minimize the critical bus bar distance, if y<0.6 h tan θ,then the portion of BB₂ along leg 2 will be equal to length y,otherwise, this portion has a length of 0.6 h tan θ. This is a generalguideline, and other rules may apply. In the illustrated embodiment, theportion of BB₂ along base 1 has a length of about 0.6 h and BB₁ alongleg 1 has a length from between 0.8-1.0 times the length of Leg 1. Inother embodiments, other lengths may be used. In one embodiment, thelength of BB₁ may be in the range of 0.4-0.8 times the length of Leg 1.In one embodiment, the length of BB₁ may be in the range of 0.5-0.7times the length of Leg 1. In one embodiment, the portion of BB₂ alongBase 1 may have a length in the range of 0.4 h-1.0 h. In one embodiment,the portion of BB₂ along Base 1 may have a length in the range of 0.6h-0.8 h. These lengths may be determined from methods described herein,such as the method described with reference to FIG. 11.

FIG. 8 is a drawing of a top view of a right trapezoid shaped devicewith bus bars in a second configuration (Configuration 2). The righttrapezoid includes two parallel opposing sides, base 1 and base 2, andtwo non-parallel opposing sides, leg 1 and leg 2. A first bus bar, BB₁,is located along base 1 and a second bus bar, BB₂, is located along leg1 and base 2. This bus bar configuration (Configuration 2) is similar tothe planar bus bar configuration used for rectangular devicesillustrated in FIGS. 4 and 1A, in that a bus bar is located along thelongest side and a bus bar is located opposing the first bus bar. Thelength of base 1 is h, the length of leg 2 is w, the length of base 2 ish₁, and the length of leg 1 is h₃. In FIG. 8, h₃=sqrt [(h−h₁)²+w²]. InFIG. 8, the critical bus bar distance is w. In some cases, the length ofthe portion of BB₁ extending along Leg 1 ranges from about 0 inches to15 inches. In one embodiment, the length of the portion of BB₁ extendingalong Leg 1 is in the range of about 0.03-0.40 times the length ofLeg 1. In one embodiment, if (h₃−w)<(−0.06w+5.48), then BB₁ does notinclude a portion along Leg 1. In the illustrated embodiment, the lengthof the portion of BB₂ extending along Leg 1 may be about h₃-w. In onecase, BB₁ may along the entire length of Base 1 and BB₂ may extend alongthe entire length of Base 2. These lengths may be determined frommethods described herein, such as the method described with reference toFIG. 11.

Certain embodiments include methods of determining whether to treat aright trapezoid (and other shapes) shaped device as a variant of a righttriangle or as a variant of a rectangle. A first method is schematicallydepicted in the diagram shown in FIG. 9. With this method, it isdetermined whether the area (A₁) required to turn the right trapezoidinto a right triangle is less than or greater than or equal to the area(A₂) required to turn the trapezoid into a rectangle. If A₁<A₂, then thebus bar configuration 1 is used as shown in FIG. 7. If A₁≥A₂, thenconfiguration 2 from FIG. 8 is used. A second method for selecting aright trapezoidal bus bar configuration is schematically depicted in thediagram shown in FIG. 10. This second method adjusts the bus bars toreduce or minimize critical bus bar distance. This second methoddetermines whether to use a particular bus bar configuration based onthe dimensions of the shape. If y≥(min(h tan θ,h)+(h₁ sin θ))/3 andh₁<(min(h tan θ,h)+(h sin θ))/3, then the bus bar configuration in FIG.7 (Configuration 1) is used, otherwise the bus bar configuration in FIG.8 (Configuration 1) is used. This method minimizes the maximum criticalBB distance. There may be a reliability advantage with this method sincelower voltage would be used to power device. These methods may providemore reliable devices since the applied voltage needed to uniformlytransition the device to ending optical states may be reduced.

Certain embodiments include a method for determining bus bar placementand lengthwise sizing involve using symmetry of the non-rectangularshape to determine the location of the bus bars. A flow chart depictingthis method is shown in FIG. 11. FIG. 12 is a diagram showing theapplication of this method to a right triangle and two right trapezoids.This method determines the lengths of each four bus bar segments, L₁-L₄,extending from two anchor points, P₀ and Q₀. This method determineslengths that reduce or minimize the difference between the bus bardistance at the weakest coloring point (presumed to be at the centroid)of the device and the bus bar distance at the strongest coloring pointof the device. In certain embodiments, the lengths of each of the fourbus bar segments are convergent lengths, that is, the lengths arecalculated each to a convergent length, where the difference between thebus bar distance at the weakest and at the strongest point is reduced orminimized. These lengths can be used to determine an optical bus barlayout. Coloring strength is defined by the sum of the distances betweena point and each of the two bus bars.

At step 1010, this method determines the centroid (i.e., geometricalcenter) of the shape designated as point O in some illustrated examples.In most cases, the centroid is assumed to be the weakest coloring pointon the colorable area of the device.

At step 1020, the method uses the centroid to define anchor points (P₀and Q₀) for bus bars on opposite sides (boundaries) of the device.First, a line is dropped from the centroid to the longest side of theshape to define P₀. Next, intersect the perpendicular line with theopposite side of the device to define Q₀. The intersections of the linewith the opposing sides of the device define the anchor points, P₀ andQ₀, for the bus bars. This line is represented by P₀-O-Q₀. The anchorpoints determine the starting sides for the bus bars.

At step 1030, the method determines values of the length of each of fourbus bar segments L₁-L₄ extending from the anchor points. In the firstiteration, the values are initialized. For example, the values may beinitialized such that the total bus bar length, L₁+L₂+L₃+L₄, is equal tothe device perimeter. FIG. 12 shows a diagram defined geometry of thebus bars for three shapes. From point P₀, a line is drawn of length L₁parallel to the first starting side to define point P₁. Another line isdrawn of length L₂ in the opposite direction from point P₀ to definepoint P₂. If the line reaches a corner before L₂ can be drawn, then theline continues past the corner along the new edge. From point Q₀, a lineis drawn of length L₃ parallel to the second starting side to definePoint Q₁. Another line is drawn of length L₄ in the opposite directionfrom Q₀ to define point Q₂. If the line reaches a corner before L₄ canbe drawn, then the line continues past the corner to the new edge. Drawa perpendicular from the centroid at point O to intersect the bus barline containing Point P₀ to define the intersection point as Point P. Ifthe bus bar extends to more than one side, then draw perpendicular linesfrom the centroid to each of the sides to define points P′, P″, P″, etc.Draw a perpendicular from the centroid at point O to intersect the busbar line containing Point Q₀ and define the intersecting point as PointQ. If the bus bar extends to more than one side, then draw perpendicularlines from the centroid to each of the sides to define points Q′, Q″,Q′″, etc.

At step 1040, the method determines the difference, D, between thedistance do between the weakest coloring point and the bus bars and thedistance d₁ between the strongest coloring point and the bus bars. Thatis, D=|d₁−d₀| is determined. To determine the bus bar distance at theweakest coloring point, a minimum distance D0_P from the centroid to thebus bar at the side containing P/P′/P″/P′″, etc. is determined and aminimum distance D0_Q from the bus bar at the side containingQ/Q′/Q″/Q′″ is determined. The maximum distance D0_P is the maximumdistance between the following pairs of points: a) O-P, b) O-P′, c)O-P″, and d) O-P′″, etc. The minimum distance D0_Q is the maximumdistance between the following pairs of points: a) O-Q, b) O-Q′, c)O-Q″, and d) O-Q′″, etc. The bus bar distance at the weakest coloringpoint, d0=D0_Q+D0_P. The bus bar distance at the strongest coloringpoint, d1, is the reduced or minimum distance between the opposite busbars anchored by points P, Q.

At step 1042, the method also determines the ratio of the total bus barlength to the perimeter R_(BB) which is the sum of the lengths of theindividual BB segments (L₁, L₂, L₃, and L₄) divided by the perimeter ofthe part (e.g. the active area of the device coating or the perimeter ofthe substrate).

At step 1050, the method determines whether the method converged to areduced or minimum difference D=|d₁−d₀| while maintaining R_(BB)>0.4. Ifthe method has not converged, the bus bar values are adjusted to newvalues and a new iteration begins by returning to step 1030. If themethod has converged, the method determines a bus bar configuration forsubstantially uniform coloration of the device from the current valuesat that iteration for the values of each of four bus bar segments L₁-L₄(step 1060). These may be termed the “convergent values” of each of thebus bar segments.

In an optional step 1070, the method determines a zone of acceptablevalues for L₁-L₄ around the convergent values determined at step 1060.These values provide a broader range of bus bar dimensions that providesubstantially uniform coloration. In some cases, the user can select oneor more sets of acceptable values in the zone that may be mostadvantageous for various reasons such as, for example, easier toproduce, improved aesthetics, etc. In optional step 1070, the zone canbe defined around the solution determined in step 1040. The zone can bedefined as one or more sets of values for L₁-L₄ within a predefined Dvalue (e.g., D<15 inches, D<20 inches, etc.) from the solutiondetermined in step 1040. In one example, the method may determine a zoneof sets of acceptable L₁-L₄ values around lengths of L₁-L₄ where D<15inches.

In one embodiment, the method may adjust the values of the lengths fromthe convergent values by small increments and calculate the difference Dbased on the adjusted values. If the calculated D is within thepredefined maximum D value, the adjusted values of the lengths arewithin the zone of acceptable values. The method may continue to adjustthe values of the lengths further from the convergent values until acertain number of sets of acceptable values are determined. In somecases, the user may provide additional input to determine whethercertain sets of values are acceptable. For example, the user may set aminimum length to be a certain value (e.g., 0.50 inches). In thisexample, the user may set this minimum based on the difficulty inmanufacturing a bus bar segment less than the minimum.

In certain embodiments, the method described with reference to FIG. 11can be used to determine a generic solution for a particular shape typethat can be applied to any shape of that type. The solution can be basedon the convergent value or an acceptable value. Some examples of genericsolutions of bus bar layouts are shown in FIGS. 13A-13C for a righttriangle and two right trapezoids. Other generic solutions are describedherein. Using these generic solutions, bus bar layouts for uniformcoloration can be determined from calculations based on the shapedimensions. For example, the solution shown in FIG. 13A provides a busbar along the right angle with a length of 0.6 times the length of leg 1and length of 0.6 times the length of leg 2. In this particular triangleshaped device, leg 1 is 90″ and leg 2 is 45″, and the BB₂ is 54″ alongleg 1 and 27″ along leg 2.

In some cases, it may be advantageous from an operations stand-point tohave the bus bar connected to the lower layer located along a continuousside, which can drive the location of the edges where the bus bars willbe configured. For example, FIG. 13C has BB₁ connected to the lowerlayer and is located on the continuous edge along base 1. BB₂ is thenlocated on the opposing non-continuous edges along Base 2 and Leg 1.

Although the bus bar layouts for right trapezoids and/or right trianglesare described with reference to certain embodiments, bus barconfigurations for other shapes (e.g., parallelogram, semicircle,quarter circle, etc.) can be designed using the techniques describedherein. Some examples of bus bar configurations designed with techniquesdescribed herein are shown in FIGS. 14A, 14B, 15, 16, 17, and 18. FIG.14A depicts an example of a first bus bar configuration for an archshaped device. FIG. 14B depicts an example of a second bus barconfiguration for an arch shaped device. FIG. 15 depicts an example of abus bar configuration for a semicircle device. FIG. 16 is an example ofa bus bar configuration for a quarter circle device. FIG. 17 depictsexamples of bus bar configurations for trapezoidal shaped devices.

FIG. 18 depicts an example of a first bus bar configuration for atriangular shaped device. Results from using different bus bar ratiosfor this configuration are shown in FIGS. 19-23. The bus bar ratio of0.60 for each side of the Bus Bar 2 may have the best balance oftransient uniformity while coloring the 30 degree corner well. FIG.19-23 are datasets showing coloration in triangle shaped electrochromicdevices having different bus bar ratios ranging from 0.50 to 0.70. A busbar ratio can refer to the ratio of the length of the bus bar to thelength of the side (of the device) having the bus bar. FIG. 20 depicts abus bar configuration with 0.50 bus bar ratio for bus bar 2. FIG. 21depicts a bus bar configuration with 0.55 bus bar ratio for bus bar 2.FIG. 22 depicts a bus bar configuration with 0.60 bus bar ratio for busbar 2. FIG. 23 depicts a bus bar configuration with 0.70 bus bar ratiofor bus bar 2.

FIG. 19 shows plots comparing coloration for a 0.60 bus bar ratio (i.e.,bus bar length=0.60 times the length of the side) with the 0.80 bus barratio (i.e., bus bar length=0.80 times the length of the side). Top plothas bus bar 2 with a 0.60 bus bar ratio. Bottom plot has bus bar 2 witha 0.80 bus bar ratio. In the top plot, a 0.60 bus bar ratio shows adifference of about 0.60 between the fastest and the slowest coloringregions when the weakest region is reaching the ending optical state. Asshown in the bottom plot, a 0.80 bus bar ratio shows a difference ofabout 1.10 between the fastest and the slowest coloring regions when theweakest region is reaching the ending optical state. The circled valuesare the areas having the maximum effective voltage. Comparing the plots,there is a location shift of the potentially overdriven locations on thedevice. In the 0.80 bus bar ratio configuration, the area with maximumeffective voltage is in the 30° corner and in the 0.60 bus bar ratioconfiguration, the area with maximum effective voltage is closer to themiddle of the triangle. FIG. 19 results show that the 0.60 bus barration configuration is less overdriven overall than the 0.80 bus barconfiguration.

After formation of an electrochromic device, edge deletion and/or laserscribing may be performed in certain embodiments. SCANLAB AG of Munich,Germany provides scanners that may be used in accordance with thedisclosed embodiments. Generally, these processes remove some or all ofthe device around a perimeter region of the device. Edge deletion canrefer to a process that removes material from the perimeter of theelectrochromic device. Edge deletion may remove the upper layer andelectrochromic layer or may remove the upper layer, electrochromiclayer(s), and the lower layer of an electrochromic device. Laserscribing can be used to isolate portions of the device, for example,portions damaged during an edge deletion process. In some illustratedexamples, an optional isolation scribe is illustrated as a “L3” scribe.The L3 scribe passes through the upper transparent conducting layer andmay penetrate one or more device layers below the TCL, including theelectrochromic layer, but does not penetrate the lower transparentconducting layer. In some illustrated embodiments, the edge deletion maybe referred to as “LED.” Although “L3” and/or “LED” areas may be shownin some illustrated examples, one or both of these features are optionaland one or both may be omitted. Some examples of edge deletion and laserscribing can be found in U.S. patent application Ser. No. 12/645,111,titled “FABRICATION OF LOW DEFECTIVITY ELECTROCHROMIC DEVICES,” filed onDec. 22, 2009, U.S. patent application Ser. No. 13/456,056, titled“ELECTROCHROMIC WINDOW FABRICATION METHODS,” filed on Apr. 25, 2012, andPCT Patent application No. PCT/US2012/068817, titled “THIN-FILM DEVICESAND FABRICATION,” filed on Dec. 10, 2012, which are hereby incorporatedby reference in their entirety.

FIG. 24A is a process flow, 2400, describing aspects of a method offabricating an electrochromic device or other optical device havingopposing bus bars, each applied to one of the conductive layers of theoptical device. The dotted lines denote optional steps in the processflow. An exemplary device, 2440, as described in relation to FIGS.24B-C, is used to illustrate the process flow. FIG. 24B provides topviews depicting the fabrication of device 2440 including numericalindicators of process flow 2400 as described in relation to FIG. 24A.FIG. 24D shows cross-sections of the lite including device 2440described in relation to FIG. 24B. Device 2440 is a rectangular device,but process flow 2400 applies to any shape of optical device havingopposing bus bars, each on one of the conductor layers. This aspect isdescribed in more detail below in relation to FIG. 24E, whichillustrates process flow 2400 as it relates to fabrication of a roundelectrochromic device.

Referring to FIGS. 24A and 24B, after receiving a substrate with a firstconductor layer thereon, process flow 2400 begins with an optionalpolishing of the first conductor layer (e.g., lower transparentconductor layer), see 2401. In certain embodiments, polishing a lowerconductor layer has been found to enhance the optical properties of, andperformance of, EC devices fabricated thereon. Polishing of transparentconducting layers prior to electrochromic device fabrication thereon isdescribed in patent application, PCT/US12/57606, titled, “Optical DeviceFabrication,” filed on Sep. 27, 2012, which is hereby incorporated byreference in its entirety. Polishing, if performed, may be done prior toan edge deletion, see 2405, or after an edge deletion in the processflow. In certain embodiments, the lower conductor layer may be polishedboth before and after edge deletion. Typically, the lower conductorlayer is polished only once.

Referring again to FIG. 24A, if polishing 2401 is not performed, process2400 begins with edge deleting a first width about a portion of theperimeter of the substrate, see 2405. In certain embodiments, thedeleted portion includes portions adjacent to all but one edge of thesubstrate. In another embodiment, the deleted portion is along a singleedge of substrate (e.g., an ITO bus bar edge). The edge deletion mayremove only the first conductor layer or may also remove a diffusionbarrier, if present. In one embodiment, the substrate is glass andincludes a sodium diffusion barrier and a transparent conducting layerthereon, e.g., a tin-oxide based transparent metal oxide conductinglayer. In the depicted embodiment, the substrate is rectangular (e.g.,the square substrate depicted in see FIG. 24B). In the embodiments ofinterest, it is typically a more complex shape. The dotted fill area inFIG. 24B denotes the first conductor layer. Thus, after edge deletionaccording to process 2405, transparent conductor of a width A is removedfrom three sides of the perimeter of substrate 2430. This width istypically, but not necessarily, a uniform width. A second width, B, isdescribed below. Where width A and/or width B are not uniform, theirrelative magnitudes with respect to each other are in terms of theiraverage width.

As a result of the removal of the first width A at 2405, there is anewly exposed edge of the lower conductor layer. In certain embodiments,at least a portion of this edge of the first conductive layer may beoptionally tapered, see 2407 and 2409. The underlying diffusion barrierlayer may also be tapered. The inventors have found that tapering theedge of one or more device layers, prior to fabricating subsequentlayers thereon, has unexpected advantages in device structure andperformance.

In certain embodiments, the lower conductor layer is optionally polishedafter edge tapering, see 2408. It has been found, that with certaindevice materials, it may be advantageous to polish the lower conductorlayer after the edge taper, as polishing can have unexpected beneficialeffects on the edge taper as well as the bulk conductor surface whichmay improve device performance (as described above). In certainembodiments, the edge taper is performed after polish 2408, see 2409.Although edge tapering is shown at both 2407 and 2409 in FIG. 24A, ifperformed, edge tapering would typically be performed once (e.g., at2407 or 2409).

After removal of the first width A, and optional polishing and/oroptional edge tapering as described above, the EC device is depositedover the surface of substrate 2430, see 2410. This deposition includesone or more material layers of the optical device and the secondconducting layer, e.g., a transparent conducting layer such as indiumtin oxide (ITO). The depicted coverage is the entire substrate, butthere could be some masking due to a carrier that must hold the glass inplace. In one embodiment, the entire area of the remaining portion ofthe first conductor layer is covered including overlapping the firstconductor about the first width A previously removed. This allows foroverlapping regions in the final device architecture.

In particular embodiments, electromagnetic radiation is used to performedge deletion and provide a peripheral region of the substrate, e.g., toremove transparent conductor layer or more layers (up to and includingthe top conductor layer and any vapor barrier applied thereto),depending upon the process step. In one embodiment, the edge deletion isperformed at least to remove material including the transparentconductor layer on the substrate, and optionally also removing adiffusion barrier if present. In certain embodiments, edge deletion isused to remove a surface portion of the substrate, e.g., float glass,and may go to a depth not to exceed the thickness of the compressionzone, if tempered. Edge deletion may be performed, e.g., to create agood surface for sealing by at least a portion of the primary seal andthe secondary seal of the spacer of an IGU. For example, a transparentconductor layer can sometimes lose adhesion when the conductor layerspans the entire area of the substrate and thus has an exposed edge,despite the presence of a secondary seal. Also, it is believed that whenmetal oxide and other functional layers have such exposed edges, theycan serve as a pathway for moisture to enter the bulk device and thuscompromise the primary and secondary seals.

Exemplary electromagnetic radiation includes UV, lasers, and the like.For example, material may be removed with directed and focused energy ator near one of the wavelengths 248 nm, 355 nm (i.e. UV), 1030 nm (i.e.IR, e.g., disk laser), 1064 nm (e.g., Nd:Y AG laser), and 532 nm (e.g.,green laser), though these examples are non-limiting. In anotherembodiment, the laser emits over a wider range of wavelengths. Forexample, the laser may be a full spectrum laser. In other cases, thelaser may emit over a narrow band of wavelengths. Laser irradiation isdelivered to the substrate using, e.g., optical fiber or open beam path.The ablation can be performed from either the substrate side or the ECfilm side depending on the choice of the substrate handling equipmentand configuration parameters. The energy density required to ablate thefilm thickness is achieved by passing the laser beam through an opticallens. The lens focuses the laser beam to the desired shape and size. Inone embodiment, a “top hat” beam configuration is used, e.g., having afocus area of between about 0.005 mm² to about 2 mm². In one embodiment,the focusing level of the beam is used to achieve the required energydensity to ablate the EC film stack. In one embodiment, the energydensity used in the ablation is between about 2 J/cm² and about 6 J/cm².

During certain laser edge delete processes, a laser spot is scanned overthe surface of the EC device, along the periphery. In one embodiment,the laser spot is scanned using a scanning F theta lens. Homogeneousremoval of the EC film is achieved, e.g., by overlapping the spots' areaduring scanning. In one embodiment, the overlap is between about 5% andabout 100%, in another embodiment between about 10% and about 90%, inyet another embodiment between about 10% and about 80%. Appropriateapparatus for undertaking LED/BPE and scribing processes is described inU.S. patent application Ser. No. 13/436,387, filed Mar. 30, 2012, titled“COAXIAL DISTANCE MEASUREMENT VIA FOLDING OF TRIANGULATION SENSOR OPTICSPATH,” which is herein incorporated by reference in its entirety.

Various scanning patterns may be used, e.g., scanning in straight lines,curved lines, etc. With these scanning patterns, various shaped sectionsmay be scanned, such as, e.g., rectangular, round, oval, polygonal,irregular, etc. or other shaped sections that can, collectively, createthe peripheral edge deletion area. In one embodiment, the scanning lines(or “pens,” i.e., lines created by adjacent or overlapping laser spots,e.g., square, round, etc.) are overlapped at the levels described abovefor spot overlap. That is, the area of the ablated material defined bythe path of the line previously scanned is overlapped with later scanlines so that there is overlap. That is, a pattern area ablated byoverlapping or adjacent laser spots is overlapped with the area of asubsequent ablation pattern. For embodiments where overlapping is used,spots, lines or patterns, a higher frequency laser, e.g., in the rangeof between about 5 KHz and about 500 KHz, may be used. In certainembodiments, the frequency is between about 8-15 kHz, for example,between about 10-12 kHz. In some other cases, the frequency may be inthe low MHz range. In order to minimize heat related damage to the ECdevice at the exposed edge (i.e. a heat affected zone or “HAZ”), shorterpulse duration lasers are used. In one example, the pulse duration isbetween about 100 fs (femtosecond) and about 100 ns (nanosecond). Inanother embodiment, the pulse duration is between about 1 ps(picosecond) and about 50 ns. In yet another embodiment, the pulseduration is between about 20 ps and about 30 ns. Pulse duration of otherranges can be used in other embodiments.

Referring again to FIGS. 24A and 24B, process flow 2400 continues withremoving a second width, B, narrower than the first width A, aboutsubstantially the entire perimeter of the substrate, see 2415. This mayinclude removing material down to the substrate (e.g., glass) or to adiffusion barrier, if present. After process flow 2400 is complete up to2415, e.g., on a rectangular substrate as depicted in FIG. 24B, there isa perimeter area, with width B, where there is none of the firsttransparent conductor, the one or more material layers of the device, orthe second conducting layer so that removing width B has exposeddiffusion barrier or substrate. In certain cases, however, there may bea small amount of conductor left after this operation. Where the amountof conductor remaining is thin enough, it does not present colorationissues. Within this perimeter area is the device stack, including thefirst transparent conductor surrounded on three sides by overlapping oneor more material layers and the second conductor layer. On the remainingside (e.g., the bottom side in FIG. 24B) there is no overlapping portionof the one or more material layers and the second conductor layer.Instead, it is proximate this remaining side (e.g., bottom side in FIG.24B) that the one or more material layers and the second conductor layerare removed in order to expose a portion (bus bar pad expose, or “BPE”),2435, of the first conductor layer, see 2420. The BPE 2435 need not runthe entire length of that side, it need only be long enough toaccommodate the bus bar and leave some space between the bus bar and thesecond conductor layer so as not to short on the second conductor layer.In one embodiment, the BPE 2435 spans the length of the first conductorlayer on that side. In some embodiments, a scribe line parallel to theBPE is created through the second conductor layer but not through thefirst conductor layer. This scribe is sometimes referred to as an L₃isolation scribe. In some embodiments, this scribe is performed in lieuof operation 2415, the removing second width B around the entireperimeter of the substrate. In another embodiment, post-deposition LEDis performed on a substrate without any pre-scribing or removal of thetransparent electronic conductor on non-busbar edges.

As described above, in various embodiments, a BPE is where a portion ofthe material layers are removed down to the lower electrode (e.g., atransparent conducting oxide (TCO) layer) or other conductive layer, inorder to create a surface for a bus bar to be applied and thus makeelectrical contact with the conductive layer. The bus bar applied can bea soldered bus bar, ink bus bar, and the like. A BPE typically has arectangular area, but this is not necessary; the BPE may be anygeometrical shape or an irregular shape. For example, depending upon theneed, a BPE may be circular, triangular, oval, trapezoidal, and otherpolygonal shapes. The BPE shape may be dependent on the configuration ofthe EC device, the substrate bearing the EC device (e.g., an irregularshaped window), or even the efficiency of the laser pattern used toablate the surface. In one embodiment, the BPE spans at least about 50%of the length of one side of an EC device. In one embodiment, the BPEspans at least about 80% of the length of one side of an EC device.Typically, but not necessarily, the BPE is wide enough to accommodatethe bus bar. In certain cases, the BPE is wide enough to allow for somespace at least between the active EC device stack and the bus bar. Incertain embodiments, the BPE is substantially rectangular, having alength approximating one side of the EC device. In one of theseembodiments, the width of the rectangular BPE between about 1 mm andabout 15 mm. In another embodiment, the width of the rectangular BPE isbetween about 1 mm and about 5 mm, for example, between about 1 mm andabout 3 mm. In another embodiment, the width of the rectangular BPE isbetween about 5 mm and about 10 mm, for example, between about 7 mm andabout 9 mm. As mentioned, a bus bar may be between about 1 mm and about5 mm wide, typically about 3 mm wide or about 2 mm wide.

As mentioned, in certain cases, the BPE is fabricated wide enough toaccommodate the bus bar's width and also leave space between the bus barand the EC device (as the bus bar should only contact the lowerconductive layer). The bus bar width may exceed that of the BPE (e.g.,where bus bar material is touching both the lower conductor and glass(and/or diffusion barrier) on area 140), as long as there is spacebetween the bus bar and the EC device or the bus bar only contacts adeactivated portion of the EC device e.g., in embodiments where there isan L3 isolation scribe. In embodiments where the bus bar width is fullyaccommodated by the BPE, that is, the bus bar is entirely atop the lowerconductor, the outer edge along the length of the bus bar may be alignedwith the outer edge of the BPE, or inset by, for example, between about1 mm and about 3 mm. Likewise, the space between the bus bar and the ECdevice is in one embodiment between about 1 mm and about 3 mm, inanother embodiment between about 1 mm and 2 mm, and in anotherembodiment about 1.5 mm. Formation of BPEs is described in more detailbelow, with respect to an EC device having a lower electrode that is aTCO layer. This is for convenience only, the lower electrode could beany suitable electrode for an optical device, transparent or not.

To make a BPE, an area of the lower (first) electrode (e.g., bottom TCO)is cleared of deposited material so that a bus bar can be fabricated onthe lower electrode. In one embodiment, this is achieved by laserprocessing which selectively removes the deposited film layers whileleaving the lower electrode exposed in a defined area at a definedlocation. In one embodiment, the relative absorption characteristics ofthe bottom electrode and the deposited layers are exploited in order toachieve selectivity during laser ablation. That is, so that the ECmaterials on the lower electrode (e.g., TCO), for example, can beselectively removed while leaving the lower electrode material intact.In certain embodiments, an upper portion of the lower electrode layer isalso removed in order to ensure good electrical contact with the busbar, e.g., by removing any mixture of lower electrode and EC materialsthat might have occurred during deposition. In certain embodiments, whenthe BPE edges are laser machined so as to minimize damage at theseedges, the need for an L₃ isolation scribe line to limit leakagecurrents can be avoided—this may eliminate a process step, while stillachieving the desired device performance.

In certain embodiments, the electromagnetic radiation used to fabricatea BPE is the same as described above for performing edge deletion. The(laser) radiation is delivered using either optical fiber or the openbeam path. The ablation can be performed from either glass side or thefilm side depending on the choice of the electromagnetic radiationwavelength. The energy density required to ablate the material isachieved by passing the laser beam through an optical lens. The lensfocuses the laser beam to the desired shape and size, e.g., a “top hat”having the dimensions described above, in one embodiment, having anenergy density of between about 0.5 J/cm² and about 4 J/cm². In oneembodiment, laser scan overlapping for fabricating a BPE can beaccomplished in a similar fashion as is described above for laser edgedeletion. In certain embodiments, variable depth ablation is used forBPE fabrication, which is described in more detail below.

In certain embodiments, e.g., due to the selective nature of therelative absorption properties of material layers in an EC device, thelaser processing at the focal plane results in some amount (betweenabout 10 nm and about 100 nm) of residual material, e.g., tungstenoxide, remaining on the exposed area of the lower conductor. Since manyEC materials are not as conductive as the underlying conductor layer,the bus bar fabricated on this residual material may not make fullelectrical contact with the underlying conductor, which can result in avoltage drop across the bus bar to lower conductor interface. Thisvoltage drop may impact coloration of the EC device as well as impactthe adhesion of the bus bar to the lower conductor. One way to overcomethis problem is to increase the amount of laser energy used in materialremoval, however, this approach may result in forming a trench at thespot overlap, which can unacceptably deplete the lower conductor. Toovercome this problem, the laser ablation can be performed above thefocal plane, i.e., the laser beam can be defocused in certainembodiments. In one embodiment, for example, the defocused profile ofthe laser beam can be a modified top hat, or “quasi top hat.” By using adefocused laser profile, the fluence delivered to the surface can beincreased without damaging the underlying TCO at the spot overlapregion. This method minimizes the amount of residual material left in onthe exposed lower conductor layer and thus allows for better electricalcontact of the bus bar with the lower conductor layer.

In some embodiments, one or more laser isolation scribes may be needed,depending upon design tolerances, material choice, and the like. FIG.24C depicts top-views of three devices, 2440 a, 2440 b and 2440 c, eachof which are variations on device 2440 as depicted in FIGS. 24B and 24D.Device 2440 a is similar to device 2440, but includes L2 scribes thatisolate first portions of the EC device along the sides orthogonal tothe sides with the bus bars. Where such L2 scribes are used, thepre-deposition removal of the lower conductor (e.g., TCO) layer may beeliminated on the L2 edges. In a particular embodiment, an L3 isolationscribe is performed on these edges in combination with pre-depositionremoval of the lower conductor layer. Device 2440 b is similar to device2440, but includes an L3 scribe isolating and deactivating a secondportion of the device between the bus bar on the first (lower) conductorlayer and the active region of the EC device. Device 2440 c is similarto device 2440, but includes both the L2 scribes and the L3 scribe.Although the scribe line variations in FIG. 24C are described inreference to devices 2440 a, 2440 b and 2440 c, these variations can beused for any of the optical devices and lites of embodiments describedherein. For example, one embodiment is a device analogous to device 2440c, but where the edge deletion does not span three sides, but ratheronly the side bearing the bus bar on the top conductor (e.g., TCO) layer(or a portion long enough to accommodate the bus bar). In thisembodiment, since there are no edge delete portions on the two sidesorthogonal to the bus bars (the right and left side of 2440 c asdepicted), the L2 scribes may be closer to these edges in order tomaximize viewable area. Depending upon device materials, processconditions, aberrant defects found after fabrication, etc., one or moreof these scribes may be added to ensure proper electrical isolation ofthe lower and upper conductor layers (electrodes) and therefore ECdevice function. Any of these devices may have a vapor barrier appliedprior to, or after, one or all of these scribes. If applied after, thevapor barrier is not substantially electrically conductive; otherwise itwould short out the device's electrodes when filling the laser scribetrenches. The above-described edge tapering may obviate the need forsuch laser isolation scribes.

Referring again to FIGS. 24A and 24B, after forming the BPE, bus barsare applied to the device, a bus bar 2 on exposed area (BPE) 2435 of thefirst (lower) conductor layer (e.g., first TCO) and a bus bar 1 on theopposite side of the device, on the second (upper) conductor layer(e.g., second TCO), on a portion of the second conductor layer that doesnot have a first conductor layer below it, see 2445. This placement ofthe bus bar 1 on the second conductor layer avoids coloration under thebus bar land other associated issues with having a functional deviceunder this bus bar 1. In this example, laser isolation scribes may notbe necessary in fabrication of the device.

FIG. 24B indicates cross-section cuts Z-Z′ and W-W′ of device 2440. Thecross-sectional views of device 2440 at Z-Z′ and W-W′ are shown in FIG.24D. The depicted layers and dimensions are not to scale, but are meantto represent functionally the configuration. In this example, thediffusion barrier was removed when width A and width B were fabricated.Specifically, perimeter area 140 is free of first conductor layer anddiffusion barrier; although in one embodiment the diffusion barrier isleft intact to the edge of the substrate about the perimeter on one ormore sides. In another embodiment, the diffusion barrier is co-extensivewith the one or more material layers and the second conductor layer(thus width A is fabricated at a depth to the diffusion barrier, andwidth B is fabricated to a depth sufficient to remove the diffusionbarrier). In this example, there is an overlapping portion, 2445, of theone or more material layers about three sides of the functional device.On one of these overlapping portions, on the second conductor layer(e.g., second TCO), bus bar 1 is fabricated. In one embodiment, a vaporbarrier layer is fabricated co-extensive with the second conductorlayer. A vapor barrier is typically highly transparent, e.g., aluminumzinc oxide, a tin oxide, silicon dioxide and mixtures thereof,amorphous, crystalline or mixed amorphous-crystalline. In thisembodiment, a portion of the vapor barrier is removed in order to exposethe second conductor layer for bus bar 1. This exposed portion isanalogous to the BPE area 2435, for bus bar 2. In certain embodiments,the vapor barrier layer is also electrically conductive, and exposure ofthe second conductor layer need not be performed, i.e., the bus bar 1may be fabricated on the vapor barrier layer. For example, the vaporbarrier layer may be ITO, e.g., amorphous ITO, and thus be sufficientlyelectrically conductive for this purpose. The amorphous morphology ofthe vapor barrier may provide greater hermeticity than a crystallinemorphology.

FIG. 24D depicts the EC device layers overlying the first conductor(e.g., TCO) layer, particularly the overlapping portion, 2445. Althoughnot to scale, cross section Z-Z′, for example, depicts the conformalnature of the layers of the EC stack and the second conductor (e.g.,TCO) layer following the shape and contour of the first conductor layerincluding the overlapping portion 2445.

In various embodiments, the operations described above may be performedin a different order, and certain operations may be excluded orperformed on fewer or different sides than mentioned. In a particularembodiment, a process flow is as follows: perform post-deposition LED on3 edges of the electrochromic lite; perform a BPE operation; perform L₃isolation scribe operation; and perform transparent electrical conductor(TEC) bus bar post-deposition LED operation.

The above-described fabrication methods are described in terms ofrectangular optical devices, e.g., rectangular EC devices. This is notnecessary, as they also apply to other shapes, regular or irregular.Also, the arrangement of overlapping device layers as well as BPE andother features may be along one or more sides of the device, dependingupon the need. Alternate design/configuration of these features aredescribed in more detail in U.S. patent application Ser. No. 13/452,032,filed Apr. 20, 2012, titled “ANGLED BUS BAR,” which is incorporated byreference herein in its entirety. As described in relation to FIGS. 24Aand 24B, the fabrications described below may also include otherfeatures such as polish of the lower conductor layer, edge taper,multi-depth ablated BPE, etc. For the sake of brevity, description ofthese features is not repeated, but one embodiment is any of the deviceconfigurations described below with one or more of the featuresdescribed in relation to FIGS. 24A and 24B.

FIG. 24E is a top view schematic drawing depicting fabrication stepsanalogous to those described in relation to the rectangular substrateshown in FIG. 24B, but on a round substrate, according to an embodiment.The substrate could also be oval or have another curved edge. Thus asdescribed previously, a first width A is removed, see 2405. The one ormore material layers and second conductor layer (and optionally a vaporbarrier) are applied over the substrate, see 2410. A second width B isremoved from the entire perimeter of the substrate, see 2415 (140 a isanalogous to 140). A BPE, 2435 a, is fabricated as described herein, see2420. Bus bars are applied, see 2425, to make device 2440 d (thus, forexample, in accord with methods described above, the at least one secondbus bar is applied to the second conducting layer proximate the side ofthe optical device opposite the at least one exposed portion of thefirst conducting layer).

In conventional laser edge delete processes for rectangular-shapedelectrochromic devices, rectangular (e.g., square) laser patterns may beused to delete material from a rectangular substrate. In this type ofprocess, the laser moves linearly, forming lines back and forth over thesurface of the device, with some uniform degree of overlap between theformed lines. The laser lines are typically parallel or perpendicular tothe local periphery of the device. Notably, where a rectangular patternis used, it is not possible to efficiently perform edge deletion onedges that are curved, or on edges that are oriented at a non-rightangle to the other edges.

Various elements are relevant when implementing a laser pattern. First,a distinction may be drawn between a laser tool and a scanner. A scanneris typically part of a laser tool. The scanner can shine and direct alaser beam according to the pattern provided to the scanner. The scanneritself is not aware of its position at a given time relative to theworkpiece. A programming code is typically used to provide instructionsthat direct the laser tool to position the scanner relative to theworkpiece. In various embodiments, this code is used to reposition thescanner after a pattern has been executed and to direct the scanner toundertake the next pattern, thereby ensuring that the scanner performsthe next pattern at the correct portion of the workpiece. The scannerreceives instructions (typically in the form of a programming code)defining a pattern or patterns that the scanner will use to shine anddirect the laser beam according to the pattern or patterns. The lasertool receives instructions detailing where to position the scannerrelative to the workpiece. These instructions may contain informationregarding the timing and positioning of various processes/components.

FIG. 25A shows an area of an EC device where a single rectangular laserpattern has removed material from the surface of the device. The lightarea 2501 is where material has been removed. The generally linearorientation of the dots in the figure indicate the linear path of thelaser spots over the device surface. When using a rectangular pattern,the laser can effectively perform LED/BPE in either the x-direction orthe y-direction, parallel to a rectangular edge of a substrate, but notas easily along a diagonal edge. FIG. 25B shows a larger area of an ECdevice where a laser pattern was repeated. Here, a rectangular patternwas performed twice, once over area 2502 and once over area 2503. Insome cases, the patterns may be repeated due to the limited opticalrange of the laser being used. Either or both the laser and workpiecemay be reoriented between subsequent pattern iterations, in certainembodiments. This type of pattern may be repeated along the periphery ofthe device, as described herein. In some embodiments, the patternfollowed by the laser may change between different edges of the device.That is, different patterns can be used for different edges. Forexample, where the device is rectangular-shaped, a first laser patternon a first edge may resemble the rectangle pattern shown in FIGS. 25Aand 25B. In one embodiment, a first rectangular laser pattern is used ontwo opposing edges that results in removal of material over an area ofapproximately 14 mm wide by about 50 mm long. A second laser pattern maybe used on adjacent edges, for example, a pattern resulting in removalover an area approximately 50 mm wide by 14 mm long (such that thedimensions are inverted with respect to the first pattern).

This configuration and pairing of patterns works well forrectangular-shaped devices. However, due to limitations inherent in arectangular laser pattern, this method is much less effective fornon-rectangular shaped devices. For example, FIG. 26A illustrates anembodiment where the device 2600 is shaped like a trapezoid and thelaser pattern is rectangular. In this case, two passes through the lasertool are required to remove all the material necessary. In a first passthrough the tool, LED is performed on edges 2602, 2604 and 2606. As theLED is performed on edge 2606, the grippers 2610 individually open anddraw back as needed to expose the surface to the laser. After the lasercompletes LED of a relevant edge portion, the grippers may individuallyre-grip the device to provide stability. The edge 2608, which is angledin the orientation of the device 2600 in the first pass, cannot undergoLED during the first pass because the rectangular pattern is oriented ina direction making it unable to follow this angled edge. Instead, thedevice 2600 must be reoriented and undergo a second pass through thelaser tool. During the second pass, material is removed from edge 2608.

This reorientation of the device may be undesirable. For example,re-orienting the device may cause misalignment of the device where evenslight misalignments can result in products which fall outside allowabletolerances. One factor which may contribute to misalignment is that itis difficult to push a device through the laser tool in a preciselyuniform direction. Generally, the device is pushed through the lasertool by applying a force to/near the portion of the device which entersthe tool last (e.g., the corner between edges 2606 and 2608 during thefirst pass, and the corner between edges 2602 and 2604 during the secondpass). Where this portion is flat (e.g., for a rectangular device), itmay be relatively much easier to push the device through in a uniform,linear manner. However, where this portion is a corner or some othernon-flat or protruding shape, it may be difficult to achieve linearmovement of the device through the tool. For example, where the force isapplied near a protruding corner, the device may rotate to some degree.Any rotation will cause material to be removed in a non-uniform fashion,which may lead to device failure. Further, re-orienting devices mayintroduce additional processing errors which arise when the grippers donot grip the lite properly, or when the scanner improperly finds astarting point (e.g., a corner/edge). Reorienting devices may also beundesirable because re-orienting may result in a device which does notphysically fit through the laser tool. For example, when lite 2600 isrotated for its second pass through the tool as described above, it maybe too tall in the y-direction to fit into the laser tool.

Certain embodiments herein utilize alternative laser patterns toovercome these limitations. For example, circular spots may be used invarious laser patterns to remove material in a variety of shapes. Inanother example, an angled rectangular laser pattern (which may use anangled rectangular spot) may be used to remove material, especiallywhere the device includes an edge that is at a non-right angle withrespect to adjacent edges. In other embodiments, the pattern may beanother non-rectangular spot pattern such as a polygonal or irregularpattern. In some implementations, these alternative patterns may be usedto remove material from specific portions of a lite, for example at acorner area. By using angled/curved/other non-rectangular patterns, LEDand BPE processes may be achieved without re-orienting and/orre-gripping for a wide variety of shapes.

FIG. 27 illustrates a single circular spot of a pattern that can be usedfor performing LED and BPE operations. For example, this circular spotcan be used in an overlapping circular pattern to remove material innearly any shape. The tangent to the inner edge of the circle (i.e., theedge of the circle facing towards the center of the lite) will definethe inner edge of the removal area. FIG. 28A shows an example of anoverlapping circle pattern used to remove material from the edges of anarched lite 2800A. This figure is not drawn to scale, and is providedmerely for the purpose of broadly illustrating overlapping circularpatterns. In certain cases, the circles may overlap more substantiallyto remove more material as needed. In the illustrated embodiment, theentire laser pattern is made of overlapping circles. FIG. 28B showsanother example of an arched lite 2800B. In this illustrated embodiment,both overlapping circular and rectangular patterns are used.

FIG. 29 illustrates an angled rectangular pattern that may be used forLED and BPE operations. With an angled rectangular pattern, the laser isable to move in any linear direction along a defined angle. In otherwords, the laser is not limited to x- and y-directional movement that istypically used with a conventional laser tool using a non-angledrectangular pattern. In some cases, a rectangular spot is used that isdefined along the angle. FIG. 30 depicts an implementation of bothangled and non-angled rectangular laser patterns that may be used toremove material from the edges of the trapezoid shaped lite 3000.

The use of non-rectangular spots and patterns and angled laser patternsmay be beneficial for several reasons. First, these alternative laserpatterns may simplify the production process, as lites do not have to bereoriented during the LED/BPE operations. By avoiding manualreorientation, losses due to such handling are reduced or eliminated.Another advantage to using non-rectangular and/or angled laser patternsmay be that they enable LED/BPE operations to be performed on curvedshapes such as circles, semi-circles, ovals, etc. and polygonal shapessuch as triangles, hexagons, octagons, trapezoids, etc. The techniquesdescribed herein permit optical devices of nearly any shape and size tobe processed

In some cases, the orientation of the spots/spot is controlled byrotating a fiber of the laser tool, and/or by passing the laser beamthrough rotatable prisms. Where a pattern is rotated but the spotsdefining the pattern are not rotated, the pattern may have a roughsaw-tooth shaped edge, for example, as shown in FIG. 31. Here, the spotshape being used is a square, oriented as shown. The collection of spotshapes at different times define the ablation area. In the illustratedexample, both the glass edge and the desired pattern edge are smooth.However, the actual ablation area does not follow the desired glassedge, because the spot shapes are not oriented at the same angle as thepattern. In this case, it is preferable to rotate the spot shape to anorientation that aligns with the pattern orientation, in order toachieve a smooth-edged ablation area.

FIG. 32 shows an embodiment illustrating how fiber rotation may be usedto rotate the orientation of a spot on a substrate. In this example, thesquare spot shape is rotated 45 degrees from a first orientation to asecond orientation where it appears as a diamond. The square spot shapesof the two orientations are the same, but they are oriented at differentdegrees. In the laser tool, a Gaussian beam may be launched into asquare core fiber. The square fiber output may be “imaged” to a filmsurface through a relay lens setup. The scanner may be used to sweep thespot shape in the x- and/or y-direction on the substrate. By rotatingthe fiber at the input coupling, the square spot shape at a firstorientation at the focal plane of the laser tool may be rotated to asecond orientation.

FIG. 33 depicts an embodiment which utilizes a dove prism to rotate theorientation of a spot shape. In this embodiment, a Gaussian beam islaunched into a square core fiber. The square fiber output is “imaged”to a film surface through a relay lens setup. A dove prism may beinserted between a collimating lens and a scanner, in the region of thecollimated beam. As the prism rotates, the orientation of the spot shaperotates at twice the rate of the prism rotation. In other words, forevery N degrees of prism rotation, the spot shape rotates 2N degrees. Inthe embodiment shown in FIG. 33, for example, the prism rotates 22.5°,while the orientation of the square spot on the substrate rotates 45°.

FIG. 34 illustrates the function of the dove prism. This type of prismis a reflective prism that may be used to invert an image. Dove prismsare formed as truncated right-angle prisms. A beam of light that entersone of the sloped faces of the prism will undergo total internalreflection along the inside of the longest face of the prism (the bottomface, as shown in FIG. 34). The image emerges from the opposite slopedface, and is vertically flipped but not laterally transposed (as only asingle reflection has taken place). When a dove prism is rotated alongits longitudinal axis, the transmitted image rotates at twice the rateof prism rotation, as mentioned above. This property allows the doveprism to rotate the image by any desired angle. In the embodiment shownin FIG. 34, the prism is rotated by 20°, and the spot shape orientationis rotated by 40°.

Although described embodiments may have bus bar configurations havingone bus bar (e.g., “Upper” bus bar) connected to an upper layer andanother bus bar (e.g., “Lower” bus bar) connected to a lower layer, thebus bars may be alternatively connected to the opposite layers in otherembodiments. In these other embodiments, the designs for the scribelines and/or BPE layers and other features may be modified toaccommodate this change to the connections to upper and lower layers.

Furthermore, although the devices the illustrated embodiments may havecertain dimensions, other dimensions can be used.

Although the foregoing has been described in some detail to facilitateunderstanding, the described embodiments are to be consideredillustrative and not limiting. It will be apparent to one of ordinaryskill in the art that certain changes and modifications can be practicedwithin the scope of the description.

1-32. (canceled)
 33. A method of determining a bus bar configuration foran optically switchable device having a non-rectangular shape, themethod comprising: calculating a summed maximum bus bar distance as adistance of a weakest coloring point on the optically switchable deviceto the first bus bar and a distance of the centroid to the second busbar; calculating a summed minimum bus bar distance of a distance of astrongest coloring point on the optically switchable device to the firstbus bar and a distance of the strongest coloring point to the second busbar; and determining lengths of a first bus bar segment and a second busbar segment of a first bus bar and lengths of a third bus bar segmentand a fourth bus bar segment of a second bus bar, wherein the lengthsare determined to approximately minimize a difference between the summedmaximum bus bar distance and the summed minimum bus bar distance. 34.The method of claim 33, further comprising calculating a centroid of thenon-rectangular shape as the weakest coloring point.
 35. The method ofclaim 33, further comprising calculating a minimum distance between thefirst bus bar and the second bus bar as the strongest coloring point.36. The method of claim 33, wherein determining the lengths of thefirst, second, third, and fourth bus bar segments includes adjusting thelengths until the difference between the summed maximum bus bar distanceand the summed minimum bus bar distance reaches convergent lengths foreach of the first, second, third, and fourth bus bar segments.
 37. Themethod of claim 36, further comprising determining one or more sets ofacceptable values of the first, second, third, and fourth bus barsegments based on the convergent lengths.
 38. The method of claim 37,wherein the acceptable values are less than 10 inches or 20 inches fromthe convergent lengths.
 39. The method of claim 38, wherein theacceptable values are also more than a minimum length.
 40. The method ofclaim 39, wherein the minimum length is about 0.50 inches.
 41. Themethod of claim 33, wherein the optically switchable device is anelectrochromic device.
 42. The method of claim 41, wherein theelectrochromic device has a first conductive layer, a second conductivelayer, and an electrochromic layer between the first and secondconductive layers; wherein the first bus bar is electrically connectedto the first conductive layer; and wherein the second bus bar iselectrically connected to the second conductive layer.
 43. The method ofclaim 33, wherein the non-rectangular shape is one of a triangle, atrapezoid, a hexagon, and an octagon.
 44. The method of claim 33,wherein the first bus bar segment and the second bus bar segment arelocated along a right angle of the non-rectangular optically switchabledevice.
 45. The method of claim 33, wherein the first bus bar segmentand the second bus bar segment are located along a right angle of thenon-rectangular optically switchable device.
 46. A method of determininga bus bar configuration for an optically switchable device having anon-rectangular shape, the method comprising: transforming thenon-rectangular shape into an effective rectangular shape; applying aplanar bus bar design to the effective rectangular shape to determinelengths of a first bus bar segment and a second bus bar segment of afirst bus bar and lengths of a third bus bar segment and a fourth busbar segment of a second bus bar for the effective rectangular shape; andinverse transforming the effective rectangular shape with the determinedlengths of the first, second, third, and fourth bus bar segments todetermine lengths of the first, second, third, and fourth bus barsegments for the non-rectangular shape.
 47. The method of claim 46,wherein the transformation is affine transformation.
 48. The method ofclaim 46, wherein the optically switchable device is an electrochromicdevice.
 49. The method of claim 48, wherein the electrochromic devicehas a first conductive layer, a second conductive layer, and anelectrochromic layer between the first and second conductive layers;wherein the first bus bar is electrically connected to the firstconductive layer; and wherein the second bus bar is electricallyconnected to the second conductive layer.
 50. The method of claim 48,wherein the non-rectangular shape is one of a triangle, a trapezoid, ahexagon, and an octagon.
 51. The method of claim 48, wherein the firstbus bar segment and the second bus bar segment are located along a rightangle of the non-rectangular optically switchable device.
 52. The methodof claim 48, wherein the first bus bar segment and the second bus barsegment are located along a right angle of the non-rectangular opticallyswitchable device.